\documentclass{book}
\usepackage{tikz}
\usetikzlibrary{tikzmark, calc}
\usepackage{array}
\usepackage{multirow}
\renewcommand{\arraystretch}{1.4}
\begin{document}
    \begin{tabular}{ccc}
        \multicolumn{2}{c}{\tikzmark{cmc}\hfill A and B\hfill\null} & C\tikzmark{dmc} \\ 
        D wider & E & F \\
    \end{tabular}
    \begin{tikzpicture}[overlay,remember picture]
    \draw (pic cs:cmc) -- (pic cs:dmc);
    \end{tikzpicture}
\end{document}
